Hi, I've never done one of these engines before so I've come to the fountain of knowledge. I've split the cases of my 66 A-65 and would like to determine if the crankshaft bushing needs replacement. I can't find an allowable clearance value in any of my manuals. I can just fit a .002" feeler gauge between the shaft and the bushing. I can't figure a way to get plastigauge in there. Is there a better way to check this?
This bike was a complete basket case when purchased so I 've never heard it run. I pulled it apart because the crankshaft endplay was .010" and I wanted to check clearances and clean the sludge trap.
What is involved in replacing the crankshaft bushing? Anything more than how it is explained in the manuals?
I agree with the .0015" clearance. Be careful stuffing feeler guages in there ...the bearing material on the vandervell is pretty soft. If you haven't got the right tools (and most of us don't), I found it pretty accurate to measure with a dial indicator ( if you have one of these). Put the foot of the indicator on top of the shaft and a well positioned prybar on the bottom and just rock the shaft and read the dial. Of course if you are replacing the bushing, the machinist should align bore the bush in the case to .0015" clearance. In fact I was checking the clearance with this method after align boring and it read .0025" . I took it back to the machinist, he disassembled, remeasured and agreed it was his mistake and made me a new bushing that was clearanced to .0015.
Re: A65 Timing Side Crank Bushing Clearance#7867 02/07/064:06 am02/07/064:06 am
I will try using the dial indicator method. I was wondering if I was ever going to find another use for that tool. The sludge trap has been cleaned and all oil holes have been blown clear. I have a 6A points plate for when it gets that far. I also have all the manuals. Great advice all.
Is the trouble of line boring necessary when using a store bought bushing? I have a picture in my head of these bikes being thrown together in a dark factory by pissed off old men using worn out machinery. How close were these tolerances when they left the factory?
Mr. Mike ,I have seen all sorts of things that I really dont comprehend, but I see it work and it gets results , but this measuring technique has me stumped . could you explain in more detail how you get these readings? I'm "assuming" the engine is in the frame and the frame is secured somehow , but where are you locating the indicator base so that it isnt affected by the prybar ? I would expect at least .001" in error as things get pryed and pushed on , I'd almost expect the frame to rock more than .001" ?? I can easily see a way to check end play with this method using the sump drain and flywheel, but I dont get where you are prying against to get repeatable readings for the bushing clearance? One other ? what are you comparing the vandervell bush with when you say it is "soft" , I know it certainly isnt hard as steel , but it is some stout material for a plain bushing , tougher than your basic brass from what I've seen, but I dont have any numbers on the alloy .
If I was in a situation where I wanted to know the clearance of the bush , and didnt have the tools to measure properly , I would simply take the whole mess to a machine shop and have it mic'd , and make sure they take measurements at several depths and locations on the OD and ID as these things tend to wear in an egg shape and you could have more than .0015 variation on the crank or in the bushing giving you loose and tight spots as the crank rotatess . A very basic rule for this is if you see a line where the crank oil hole rides in the bush , and you can even feel the ridge , it is ready to be replaced , especially since it wont be tore down that far again until something serious happens. there are loads of tips for keeping these engines happy,and quite a few simple but effective mods for making them reliable , if you are willing to spend a few $$ and some time it can make the difference between loving and hating that bike .
Unless you have a known history from new to worn out with a specific crank/bushing, not sure what value the dial indicator thing is. It will not give actual clearances in the bearing. You will be measuring beyond the bearing, which will magnify movement of the crank/bushing clearance. You might get an idea, but I would not use this as an accurate gauge of actual bearing clearance. The only correct way to do that is physcial measurement of the pieces.
oldfool sez >>Is the trouble of line boring necessary when using a store bought bushing? I have a picture in my head of these bikes being thrown together in a dark factory by pissed off old men using worn out machinery. How close were these tolerances when they left the factory?<< - Yes it is at times necessary to check alignment. Some were not that good new. I think the picture you have in your head is accurate. I also think it is why BSA developed a reputation. These motors require care in assembling the bottom end. Do it right, they work well. Do it wrong or poorly, they are troublesome.
Pissed off old men in a dark factory building engines in volume was not a good thing. You can do better. Actually, done right, you will be surpised how good a BSA unit twin can be.
Life is too short to drink cheap, bad beer.
Re: A65 Timing Side Crank Bushing Clearance#7870 02/07/0610:30 pm02/07/0610:30 pm
Bonzo and Rich, Old fool First of all I agree the very best way is to have a machinist with all the right measuring tools measuring journals and bushes for proper clearances. As far as the align boring goes. Not every bore in a set of cases is true within tenths (tens of thousandths). Thats what you want By align boring the bushing from assembled cases, you can get a near perfectly true bore on a good jig boring machine. It will be both parallel and axially true. I think this is the single most important step. If you get this right, the clearance right, and the endplay right, i think it will run long and well. I think BSA got a bad start with a cumbersome setup procedure and disgruntled workers. Rich is right, you can do better. Now on using a dial to measure clearance. It is an approximation, but I have found it to be pretty darn accurate. I have done it both in the frame and out of the frame. I use a 3x4 piece of angle iron rigidly clamped to the case (out of frame). I mount a mag base indicator to the angle iron and then thru the attachment devices, put the foot of the indicator on top of the shaft. I then use a small prybar levering off one of the oil pump studs to lift the crankshaft and watch my indicator. You want the indicator to be vertical and the force lifting to be vertical. I measured .0035 (I am doing a little guessing at the tenths), and, afterwards, with the bushing bored to .0015 clearance by the machinist, i measured exactly the same .015 with the method I described. My method might read a little less than actual, but not much, and I can surely tell the difference between .0015 and .0025. I use the same technique to measure endplay.
It is sort of like measuring piston skirt clearance with feeler gauges. It isn't as accurate as a dial bore gauge. but it is a good way to check the machinists bore job and piston fit. I always double check the machinist's work. He might be the best around but their minds wander just like ours when we are working, and mistakes happen. This is not rocket science, but I don't assume anything is right, I try to pay attention to the details, and be careful and patient. I have slapped some stuff together in my day to get going, but I don't fold to that pressure much anymore.
On the soft bearing material: the shells are hard steel. The bronze/lead/tin alloy that the journal rides on is quite soft. It is soft enough to provide embedability of particles...great for unfiltered applications...it saves the crank. With a filter system, the solid one piece bushings might even last longer. I dunno. I have a homemade bushing in my A65. It is definitely harder thatn the vandervell. I don't know the exact alloy, but the machinist has used it in pulling tractor bearings for years.
Hope this answer the questions.
Re: A65 Timing Side Crank Bushing Clearance#7871 02/10/063:29 am02/10/063:29 am
As a quick test I ran my finger over the inside of the bushing. There is an 'ever so slight' ridge around the middle where the oil groove lies. It looks to me that I'll be looking to replace the bushing. I have a local automotive machine shop that had ground the crank for my pickup. Is there anything special a machine shop needs to know to line bore a new bushing? Should I look for a pissed off old man in the back room? Al
Oldfool, You probably want a machinist the has some experience in this. My man would set the bushing side down on a set of precision parallels. It is probably a good idea to check the perpendicularity of the cylinder base surface to the case. You must also bolt up the top half of the case tightly. He then brings his spindle with an indicator mounted and clocks up on the primary side bore as a reference. He then disassembles the top of the case and drops the head down to the bushing to bore it. At this point you can check to see if the bush is true with the primary bore. If it is off a few thousandths, he can make it near perfect....however if it is way off like .010 or more you may never get it right. If the bush is not bored true it will show up in motor assembly. If there is the slightest bit of increased resistance when spinning the crank after torquing the case bolts, there is misalignment and the crank will likely wear the bushing quickly with a subsequent loss of oil pressure. Some rebuilders just hone or ream the bush. This does not ensure it is running true. If you are absolutely sure the bores are true and the bushing is Concentric, you can get away with honing or reaming to clearance. My guess is a lot of BSA's left the factory with poor clearances and endplay not properly set. It is is almost impossible to get endplay set right without disassembling at least twice If you get the crank is right and the bearing clearances correct, the rest is duck soup.
Re: A65 Timing Side Crank Bushing Clearance#7873 02/11/061:44 pm02/11/061:44 pm